Pathogenic microorganisms such as bacteria, fungi, viruses, and bacterial spores are responsible for a plethora of human and animal ailments. In addition to vegetatively growing bacteria, bacteria of the Bacillus genus and others form stable spores that resist harsh conditions and extreme temperatures. For example, contamination of farmlands with B. anthracis can lead to a fatal disease in domestic, agricultural, and wild animals, as well as in humans in contact with infected animals or animal products. B. anthracis infection in humans is no longer common due to effective animal controls that include vaccines, antibiotics, and appropriate disposal of infected livestock. However, animal anthrax infection still represents a significant problem due to the difficulty of decontaminating land and farms. Moreover, B. anthracis spores can be used as a biological weapon. While an anthrax vaccine is available and can be used for the prevention of classic anthrax, genetic mixing of different bacterial strains can render it ineffective.
Other members of the Bacillus genus are also reported to be etiological agents for many human diseases. B. cereus is a common pathogen involved in food borne diseases due to the ability of the spores to survive cooking procedures. It is also associated with local sepsis, wound and systemic infection.
Although antibiotic and antimicrobial therapy is very effective and a mainstay of modern medicine, these therapies suffer from several disadvantages. For example, bacterial strains can develop antibiotic resistance. A person infected with an antibiotic resistant strain of bacteria faces serious and potentially life-threatening consequences because antibiotics cannot eliminate the infection. Pneumococci, which cause pneumonia and meningitis, Salmonella and E. coli which cause diarrhea, and enterococci which cause blood stream, surgical wound, and urinary tract infections can all develop antibiotic resistance resulting in fatal infections.
Moreover, antibiotics are not effective in eliminating or inactivating bacterial spores and viruses. Disinfectants and biocides, such as sodium hypochlorite, formaldehyde and phenols can be effective against bacterial spores, but are not well suited for decontamination of the environment, equipment, or casualties. The toxicity of these compounds can result in tissue necrosis and severe pulmonary injury following contact or inhalation of volatile fumes. Furthermore, the corrosive nature of commonly used disinfectants and biocides renders them unsuitable for decontamination of sensitive equipment.
Viruses are additional pathogens that infect human and animals which currently lack effective means of inactivation. For example, influenza A virus is a common respiratory pathogen widely used as a model system to test anti-viral agents in vitro and in vivo. The envelope glycoproteins of influenza A, hemagglutinin (HA) and neuraminidase (NA), which determine the antigenic specificity of viral subtypes, mutate readily, rendering antibodies incapable of neutralizing the virus. Current anti-viral compounds and neuraminidase inhibitors are minimally effective and viral resistance is common.